ABSTRACT. Stenocoris (Stenocoris) schaeferi, a new species of Alydidae (Micrelytrinae: Leptocorisini) from Argentina, is described and illustrated. Lyrnessus geniculatus (Guérin-Méneville) and Stenocoris (Oryzocoris) furcifera (Westwood) are registered from Argentina for the first time. A key and a distributional map to the Argentinean Leptocorisini are also provided.

The Alydidae are usually elongate and slender with disproportionately large heads; they are commonly referred to as broad-headed bugs. The family is mainly distributed in the Old World and is poorly represented in the New World. According to Schaefer (2004), the family contains 53 genera of which 22 occur in the New World. Among them, only three are represented in both theOld and New World (ie., Alydus Fabricius, Megalotomus Fieber, and Stenocoris Burmeister). Schaefer (1999) established the following classification: Alydinae and Micrelytrinae, both with two tribes; the first containing Alydini and Daclerini and the second, Leptocorisini and Micrelytrini. The Leptocorisini has six genera, and is represented in all major zoogeographical regions. Members of the tribe are quite elongate and feed mainly on grasses(Schaefer, 1980; Schuh & Slater, 1995); some constitute serious pests of rice in the Old World (Schaefer, 2004). Two genera are known from the New World and are exclusively distributed in the Neotropical Region: Lyrnessus Stål, a monotypic genus, and Stenocoris Burmeister which is divided into several subgenera. In the Neotropical Region only two subgenera are known: Stenocoris (Stenocoris) Burmeister with species distributed in Africa and the New World, and Stenocoris (Oryzocoris) Ahmad only with species in the New World. Up to now information about Argentinean Alydidae has been fragmentary; the only attempt to present a unified compilation is Kormilev's (1950) review of the Micrelytrini (formerly Micrelytrinae). To date the only leptocorisine known from Argentina was Stenocoris (Oryzocoris) fabricii Ahmad. In this contribution, a new Stenocoris is described, new country records are given, and a key and a distributional map to the Argentinean Leptocorisini are also provided.

MATERIAL AND METHODS

The material examined is deposited in the Museo de La Plata, La Plata, Argentina (MLP) and the Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina (MACN). Measurements are given in millimeters. The description and illustrations of the male genitalia correspond to the male paratype from Corrientes.

We thank Carl Schaefer (Department of Ecology and Evolutionary Biology, University of Connecticut) for the critical reading of the manuscript, and to the División Zoología Invertebrados (Museo de La Plata, La Plata, Argentina) for providing the photographic equipment used. This study was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina, and the following grant: PIP 0255 (2010-2012).